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DESIGN OF A KNOWLEDGE-BASED CONTROLLER FOR INTELLIGENT CONTROL-SYSTEMS

IEEE TRANSACTIONS ON SYSTEMS MAN AND CYBERNETICS 1991年第2期21卷 368-375页

作者： SHIN, KG CUI, XZ Real-Time Computing Laboratory Department of Electrical Engineering and Computer Science University of Michigan Ann Arbor MI USA

A hierarchical knowledge-based controller is proposed to improve the performance of complex control systems, such as robots. Unlike parameter- and performance- adaptive controllers, this controller is designed only to modify the reference input of a lower-level servo controller. Because the internal parameters and structure of the lower-level controller are not affected, commercial servo controllers can be made to perform more sophisticated tasks than originally intended. The principle of the knowledge-based controller, modification of the reference input, knowledge representation, existence of the solution, and analyses of the controller's stability and tracking error are described in detail. A self-tuning multiple-step predictor is designed as part of the controller to eliminate the undesirable effects of system time delay. Both linear and nonlinear example control systems are tested via extensive simulations and have all shown promising performances.

关键词： servo controller control systems reference input intelligent control system internal parameter Controllers undesirable effects

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Optimal load sharing in distributed real-time systems 6

Optimal load sharing in distributed real-time systems

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6th Distributed Memory computing Conference, DMCC 1991

作者： Chang, Yi-Chieh Shin, Kang G. Real-Time Computing Laboratory Department of Electrical Engineering and Computer Science University of Michigan Ann ArborMI48109-2122 United States

ISBN: (纸本)0818622903

In hard real-time systems, the problem of scheduling periodic tasks to meet their deadlines has been studied extensively, but scheduling aperiodic tasks has been addressed far less, due mainly to their uncertain arrivals. The main intent of this paper is to derive an approximate, closed-form solution for the decentralized, dynamic load sharing (LS) problem treated in our early paper [1], Based on the derived solutions, we show that the probability of missing task deadlines can be kept below any required level while minimizing the communication overhead resulting from task transfers and state-information collection. Specifically, "optimal" threshold patterns and buddy set sizes are derived for different system loads by minimizing the communication overhead subject to a constraint of keeping the probability of missing task deadlines below any given level. (One can also derive optimal solutions by minimizing the probability of missing deadlines while keeping the communication overhead below a specified level.). © 1991 IEEE.

关键词： Probability

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Effective load sharing in distributed real-time systems 3

Effective load sharing in distributed real-time systems

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Proceedings of the Third IEEE Symposium on Parallel and Distributed Processing

作者： Shin, K.G. Hou, C. Real-Time Computing Laboratory Department of Elec. Engr. and Computer Science University of Michigin Ann Arbor 48109-2122 MI United States

ISBN: (纸本)0818623101

In a distributed real-time system, temporary uneven task arrivals among the nodes may cause some tasks to miss their deadlines even if the overall system has the capacity to meet the deadlines of all tasks. In this paper, an effective load sharing (LS) scheme is proposed as a solution to this problem. Upon arrival of a task at a node, the node determines whether or not it can complete the task in time under the minimum-laxity-first-served policy. If the task cannot be guaranteed or if guarantees of some other tasks are to be violated due to the insertion of this task into the existing schedule, the node looks up the list of loss-minimizing decisions, and determines the best node among a set of nodes in its physical proximity, called its buddy set, to which the task(s) may be transferred. This list of decisions is periodically updated using Bayesian decision analysis and prior/posterior state distributions. These probability distributions are derived from the information collected via time-stamped state-region change broadcasts within each buddy set. The performance of the proposed scheme is evaluated via simulation along with five other schemes. The proposed scheme is shown to outperform all but perfect LS scheme in (i) meeting task deadlines and (ii) tolerating the delays in state-information collection and task transfer. © 1991 IEEE.

关键词： Probability distributions

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Load sharing in hypercube multicomputers in the presence of node failures

Load sharing in hypercube multicomputers in the presence of ...

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International Symposium on Fault-Tolerant computing (FTCS)

作者： Y.-C. Chang K.G. Shin Real-Time Computing Laboratory Department of Electrical Engineering and Computer Science University of Michigan USA

Two important issues associated with load sharing (LS) in hypercube multicomputers are discussed and analysed: (i) ordering fault-free nodes as preferred receivers of overflow tasks and (ii) developing an LS mechanism to handle node failures. The authors previously (1989) proposed to order the nodes in each node's proximity into its preferred list of receivers for the purpose of LS in distributed real-time systems. However, the occurrence of node failures will destroy the original structure of a preferred list if the failed nodes are simply dropped from the list. Three algorithms are proposed to modify the preferred list to retain its original features. Based on the modified preferred lists, node failures can be tolerated by equipping each node with a backup queue which stores and updates the arriving/completing tasks at its most preferred node. Simulation results show that this approach, despite its simplicity, can greatly reduce the number of task losses compared to approaches that do not use backup queues.< >

关键词： Hypercubes real time systems Broadcasting Fault tolerance Laboratories Failure analysis Algorithm design and analysis Delay time factors

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Generating Synthetic Workloads for real-time Systems

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IFAC Proceedings Volumes 1991年第2期24卷 103-105页

作者： D.L. Kiskis K.G. Shin Real-Time Computing Laboratory Department of Electrical Engineering and Computer Science The University of Michigan Ann Arbor MI 48109-2122 USA

In this paper, we describe a software system which generates synthetic workloads for use in the performance evaluation of distributed real-time computer systems. The software system consists of a high-level description language and its compiler. The language provides a flexible, easy-to-use description of the structure and behavior of the real-time workload. The compiler, called a synthetic workload generator (SWG), uses this description to produce an executable synthetic workload (SW). The SW may then be used to drive the system under evaluation while measurements are being made.

关键词： computer selection and evaluation real-time computer systems software tools specification languages

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Intelligent Coordination of Multiple Systems with Neural Networks

Intelligent Coordination of Multiple Systems with Neural Net...

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American Control Conference (ACC)

作者： Xianzhong Cui Kang G. Shin Real-Time Computing Laboratory Department of Electrical and Computer Science University of Michigan Ann Arbor MI USA

Many control applications require cooperation of two or more independently designed, separately located, but mutually affecting, subsystems. In addition to the good behavior of each subsystem, effective coordination of these subsystems is very important to achieve the desired overall system peformance. However, such coordination is very difficult to accomplish due mainly to the lack of precise system models and/or dynamic parameters as well as the lack of efficient tools for system analysis, design, and real-time computation of optimal solution. In this paper, we propose a new multiple-system coordinator which combines the techniques of intelligent control and neural networks, and forms the high-level coordinator in a hierarchical structure. The basic idea is to estimate the effects of the control commands to subsystems using a predictor and modify these commands using a knowledge-based coordinator so as to achieve tie desired performance. The predictor is designed for multiple-input, multiple-output systems using neural networks. The knowledge-based coordinator is responsible for knowledge acquisition and representation, inference process, and the overall system stability. Because the internal structure and parameters of the low level are not affected by using the proposed method, some commercially-designed servo controller for single systems can be coordinated to perform more sophisticated tasks for multiple systems than originally intended.

关键词： Intelligent networks Neural networks Control systems Servomechanisms Humans Neodymium Intelligent structures Hidden Markov models System performance Decision trees

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Design of an Industrial Process Controller using Neural Networks

Design of an Industrial Process Controller using Neural Netw...

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American Control Conference (ACC)

作者： Xianzhong Cui Kang G. Shin Real-Time Computing Laboratory Department of Electrical Engineering and Computer Science University of Michigan Ann Arbor MI USA

There are many problems in industrial process control systems due to a long system response delay, dead-zone and/or saturation of the actuator mechanisms, uncertainties in the system model and/or parameters, and process noise. To overcome these problems, an adaptive controller is designed using neural networks and tested extensively via simulations. One of the key problems in designing such a controller is to develop an efficient training algorithm. Neural networks are usually trained using the output errors of the network, instead of using the output errors of the controlled plant. However, when a neural network is used to control a plant directly, the output errors of the network are unknown, since the desired control actions are unknown. In this paper, we propose a simple training algorithm for a class of nonlinear systems, which enables the neural network to be trained by the output errors of the controlled plant. The only a priori knowledge of the controlled plant is the direction of its output response. A detailed analysis of the algorithm is presented and the corresponding theorems are proved. Due to its simple structure and algorithm, and good performance, the proposed controller has high potential for handling difficult problems in industrial process control systems.

关键词： Industrial control Process control Neural networks Error correction Electrical equipment industry Algorithm design and analysis Control systems Delay systems Actuators Uncertainty

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Probabilistic clock synchronization in large distributed systems

Probabilistic clock synchronization in large distributed sys...

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International Conference on Distributed computing Systems

作者： A. Olson K.G. Shin Real-Time Computing Laboratory Department of Electrical Engineering and Computer Science University of Michigan Ann Arbor MI USA

Synchronization algorithm is proposed which uses one of two probabilistic techniques to estimate remote clock values, and uses an interactive convergence algorithm on the resulting estimates to adjust the local clock. The algorithm does not require master/slave clocks and reduces the number of messages needed. As a result it is suitable for use in large distributed systems.< >

关键词： Clocks Synchronization Hardware Master-slave Contracts real time systems Distributed computing Laboratories NASA Software algorithms

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Collision avoidance in a multiple-robot system using intelligent control and neural networks

Collision avoidance in a multiple-robot system using intelli...

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IEEE Conference on Decision and Control

作者： K.G. Shin X. Cui Real-Time Computing Laboratory Department of Electrical Engineering and Computer Science University of Michigan Ann Arbor MI USA

A new hierarchical collision avoidance scheme is proposed to coordinate multiple robots in a common workspace by combining the techniques of intelligent control and neural networks (NNs). The high level in the hierarchy is formed by a knowledge-based coordinator (KBC) and an NN-based predictor, and the low level consists of the robots to be coordinated. The authors state the problem of coordinating multiple robots for collision avoidance and the basic principles of the KBC. The knowledge acquisition and representation of collision detection and avoidance for both cylindrical- and revolute-type robots are discussed. Design of the NN-based predictor and the KBC is summarized. The proposed scheme was tested extensively via simulations for both types of robots, showing promising performance.< >

关键词： Collision avoidance Intelligent networks Intelligent control Neural networks Robot kinematics Path planning Service robots Robotic assembly Trajectory Servomechanisms

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Optimal Load Sharing In Distributed real-time Systems

Optimal Load Sharing In Distributed Real-time Systems

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Distributed Memory computing Conference

作者： Yi-Chieh Chang Kang G. Shin Real-Time Computing Laboratory Department of Electrical Engineering and Computer Science University of Michigan Ann Arbor MI USA

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